The present invention is directed to plastic containers such as bottles having side walls of substantially uniform thickness having decorative features intended to give the appearance of non-uniform thickness. The present invention is particularly directed to such bottles which are intended to contain liquids under elevated pressure such as carbonated beverages.
Historically many glass bottles intended to contain a specific brand of a liquid product, for example a specific brand of a carbonated beverage, were specifically designed to include patterns generally obtained by variations in wall thickness. The specific designs often came to have trademark significance with respect to the particular liquid product sold in such a bottle. As the glass containers were replaced with plastic containers, particularly single use containers, cost constraints required that the plastic container side wall thickness be maintained as thin as possible. The substantial variations in side wall thickness used in glass to generate the designed patterns proved to be economically impossible in plastic. While many products resorted to generic bottles devoid of surface features thus having no trademark significance, the demand for bottles having such features continued but was largely unsatisfied.
Some attempts were made to create bottles having such surface features by simply molding a container having a uniform side wall thickness and an outer surface matching the outer surface of the previously used glass container. When such bottles were used for liquids at non-elevated pressures, the bottles generally retained the intended appearance. However, when such bottles were used for liquids at super atmospheric pressures, such as carbonated beverages, the internal pressure within the bottle substantially obliterated the surface features unless the sidewall thickness of the bottle was significantly increased which made the bottle economically unsatisfactory. As a result, little if any trademark significance was attributed by the purchasing public to the current shape of the bottle, and historically important trademarks were decreasingly used. The possible loss through disuse of such trademarks was unacceptable and demand remained for a low cost bottle having a satisfactory reproduction of the old glass bottle designs.